Fan variable area nozzle with cable actuator system

ABSTRACT

An assembly for pivoting a flap according to an exemplary aspect of the present disclosure includes, among other things, a structure is mounted at least partially around an axis. The structure is attached to a pivotable flap arranged to define a nozzle area. A cable passes through an orifice defined by the flap. An actuator system is operable to mechanically retract the cable therein to lessen the nozzle area and mechanically extend the cable to enable the flow to increase the nozzle area. The actuator system is engaged with the cable. A segment of the cable, opposite the actuator system, is attached to a fixed structure. A method of providing a variable fan exit area is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/441,562, filed Mar. 17, 2009, which is a National Phase Applicationof PCT Application No. PCT/US06/39049 filed on Oct. 12, 2006.

BACKGROUND

The present invention relates to a gas turbine engine, and moreparticularly to a turbofan gas turbine engine having a cable driven fanvariable area nozzle structure within the fan nacelle thereof.

Conventional gas turbine engines include a fan section and a core enginewith the fan section having a larger outer diameter than that of thecore engine. The fan section and the core engine are disposedsequentially about a longitudinal axis and are enclosed in a nacelle. Anannular path of primary airflow passes through the fan section and thecore engine to generate primary thrust.

Combustion gases are discharged from the core engine through a primaryairflow path and are exhausted through a core exhaust nozzle. An annularfan flow path, disposed radially outwardly of the primary airflow path,passes through a radial outer portion between a fan nacelle and a corenacelle and is discharged through an annular fan exhaust nozzle definedat least partially by the fan nacelle and the core nacelle to generatefan thrust. A majority of propulsion thrust is provided by thepressurized fan air discharged through the fan exhaust nozzle, theremaining thrust provided from the combustion gases is dischargedthrough the core exhaust nozzle.

The fan nozzles of conventional gas turbine engines have fixed geometry.The fixed geometry fan nozzles are suitable for take-off and landingconditions as well as for cruise conditions. However, the requirementsfor take-off and landing conditions are different from requirements forthe cruise condition. Optimum performance of the engine may be achievedduring different flight conditions of an aircraft by varying the fanexhaust nozzle for the specific flight regimes.

Some gas turbine engines have implemented fan variable area nozzles. Thefan variable area nozzle provides a smaller fan exit nozzle diameterduring cruise conditions and a larger fan exit nozzle diameter duringtake-off and landing conditions. The existing variable area nozzlestypically utilize relatively complex mechanisms that increase engineweight to the extent that the increased fuel efficiency benefits gainedfrom fan variable area nozzle are negated.

Accordingly, it is desirable to provide an effective, lightweight fanvariable area nozzle for a gas turbine engine.

SUMMARY

A nacelle assembly for a gas turbine engine according to an example ofthe present disclosure includes a core nacelle defined about an axis forallowing flow to pass therethrough. A fan nacelle is mounted at leastpartially around the core nacelle. The fan nacelle has a fan variablearea nozzle that defines a fan exit area between the fan nacelle and thecore nacelle. The nozzle has a plurality of pivotable flaps pivotableabout a pivot defined by each of the flaps. A cable passes through anorifice defined by at least one of the flaps. An actuator system isoperable to mechanically retract the cable therein pivoting at least oneof the flaps about the pivot to lessen the fan exit area andmechanically extend the cable to enable the flow to pivot at least oneof the flaps about the pivot and increase the fan exit area. Theactuator system is engaged with the cable. A segment of the cable,opposite the actuator system, is attached to a fixed structure.

In a further embodiment of any of the foregoing embodiments, there isone actuator system for the plurality of flaps.

In a further embodiment of any of the foregoing embodiments, theactuator system includes a spool configured to spool and unspool thecable.

In a further embodiment of any of the foregoing embodiments, spooling ofthe cable around the spool decreases the fan nozzle exit area.

In a further embodiment of any of the foregoing embodiments, unspoolingof the cable around the spool increases the fan nozzle exit area.

In a further embodiment of any of the foregoing embodiments, the cableis strung through one of the plurality of flaps intermediate a firstfixed structure of the fan nacelle and a second fixed structure of thefan nacelle.

In a further embodiment of any of the foregoing embodiments, the firstfixed structure of the fan nacelle and the second fixed structure of thefan nacelle include a rib of the fan nacelle.

In a further embodiment of any of the foregoing embodiments, the fanvariable area nozzle includes a multiple of flap sets. Each of the flapsets is separately driven by a respective cable and actuator of theactuator system to adjust the fan variable area nozzle.

In a further embodiment of any of the foregoing embodiments, each flapset corresponds to a circumferential sector of the fan variable areanozzle.

In a further embodiment of any of the foregoing embodiments, there arefour circumferential sectors.

In a further embodiment of any of the foregoing embodiments, a gearsystem is driven by a core engine. A fan is driven by the gear systemabout the axis.

In a further embodiment of any of the foregoing embodiments, theactuator system includes an electromechanical actuator.

In a further embodiment of any of the foregoing embodiments, theactuator system comprises a rotary hydraulic actuator.

An assembly for pivoting a flap, the assembly disposed about an axisalong which a flow passes from an upstream direction to a downstreamdirection, the assembly including a structure mounted at least partiallyaround the axis. The structure is attached to a pivotable flap arrangedto define a nozzle area. The pivotable flap is pivotable about a pivotat the structure. A cable is engaged with a first fixed engagement pointof the structure, the cable passing through an orifice defined by theflap. An actuator system is operable to mechanically retract the cabletherein to lessen the nozzle area and mechanically extend the cable toenable the flow to urge the flap to increase the nozzle area. Theactuator system is engaged with the cable. A segment of the cable,opposite the actuator system, is attached to a fixed structure.

In a further embodiment of any of the foregoing embodiments, theactuator system includes a spool engaged with the cable.

In a further embodiment of any of the foregoing embodiments, the cableis strung through the orifice intermediate the first fixed engagementpoint and a second fixed engagement point of the structure.

A method of providing a variable fan exit area of a high-bypass gasturbine engine includes the steps of locating a fan variable area nozzleto define a fan nozzle exit area between a fan nacelle and a corenacelle, and disposing a cable through at least one nacelle engagementpoint of the fan nacelle and through at least one flap engagement pointof the fan variable area nozzle. The method includes the steps ofproviding an actuator system that engages with the cable, and activatingor deactivating the cable engaged with the fan variable area nozzle tovary the fan nozzle exit area to adjust fan bypass airflow. Deactivatingthe cable extends the cable to enable the flow to urge the flaps toincrease the area.

In a further embodiment of any of the foregoing embodiments, the step ofdisposing a cable includes activating the cable to converge the fannozzle exit area during cruise flight condition.

In a further embodiment of any of the foregoing embodiments, the step ofdisposing a cable includes engaging a first end of the cable at a spooland a second end of the cable at the fixed attachment point. The cablebetween the first and second ends is received in an orifice defined atthe flap engagement point.

In a further embodiment of any of the foregoing embodiments, theactuator system is a rotary hydraulic actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

FIG. 1A is a general perspective view an exemplary turbo fan engineembodiment for use with the present invention;

FIG. 1B is a perspective partial fragmentary view of the engine;

FIG. 1C is a rear view of the engine;

FIG. 2A is a perspective partial phantom view of a section of the FVAN;and

FIG. 2B is an expanded view of one flap assembly of the FVAN.

FIG. 2C is a partial phantom view of a section of the FVAN.

DETAILED DESCRIPTION

FIG. 1A illustrates a general partial fragmentary schematic view of agas turbofan engine 10 suspended from an engine pylon P within an enginenacelle assembly N as is typical of an aircraft designed for subsonicoperation.

The turbofan engine 10 includes a core engine within a core nacelle 12that houses a low spool 14 and high spool 24. The low spool 14 includesa low pressure compressor 16 and low pressure turbine 18. The low spool14 drives a fan section 20 connected to the low spool 14 through a geartrain 22. The high spool 24 includes a high pressure compressor 26 andhigh pressure turbine 28. A combustor 30 is arranged between the highpressure compressor 26 and high pressure turbine 28. The low and highspools 14, 24 rotate about an engine axis of rotation A.

The engine 10 is preferably a high-bypass geared turbofan aircraftengine. Preferably, the engine 10 bypass ratio is greater than ten (10),the fan diameter is significantly larger than that of the low pressurecompressor 16, and the low pressure turbine 18 has a pressure ratio thatis greater than 5. The gear train 22 is preferably an epicyclic geartrain such as a planetary gear system or other gear system with a gearreduction ratio of greater than 2.5. It should be understood, however,that the above parameters are only exemplary of a preferred gearedturbofan engine and that the present invention is likewise applicable toother gas turbine engines.

Airflow enters a fan nacelle 34 which at least partially surrounds thecore nacelle 12. The fan section 20 communicates airflow into the corenacelle 12 to power the low pressure compressor 16 and the high pressurecompressor 26. Core airflow compressed by the low pressure compressor 16and the high pressure compressor 26 is mixed with the fuel in thecombustor 30 where is ignited, and burned. The resultant high pressurecombustor products are expanded through the high pressure turbine 28 andlow pressure turbine 18. The turbines 28, 18 are rotationally coupled tothe compressors 26, 16 respectively to drive the compressors 26, 16 inresponse to the expansion of the combustor product. The low pressureturbine 18 also drives the fan section 20 through the gear train 22. Acore engine exhaust E exits the core nacelle 12 through a core nozzle 43defined between the core nacelle 12 and a tail cone 32.

The core nacelle 12 is supported within the fan nacelle 34 by structure36 often generically referred to as an upper and lower bifurcation. Abypass flow path 40 is defined between the core nacelle 12 and the fannacelle 34. The engine 10 generates a high bypass flow arrangement witha bypass ratio in which over 80 percent of the airflow entering the fannacelle 34 becomes bypass flow B. The bypass flow B communicates throughthe generally annular bypass flow path 40 and is discharged from theengine 10 through a fan variable area nozzle (FVAN) 42 (also illustratedin FIG. 1B) which varies an effective fan nozzle exit area 44 betweenthe fan nacelle 34 and the core nacelle 12.

Thrust is a function of density, velocity, and area. One or more ofthese parameters can be manipulated to vary the amount and direction ofthrust provided by the bypass flow B. The FVAN 42 changes the physicalarea and geometry to manipulate the thrust provided by the bypass flowB. However, it should be understood that the fan nozzle exit area 44 maybe effectively altered by methods other than structural changes.Furthermore, it should be understood that effectively altering the fannozzle exit area 44 need not be limited to physical locationsapproximate the end of the fan nacelle 34, but rather, may include thealteration of the bypass flow B at other locations.

The FVAN 42 defines the fan nozzle exit area 44 for discharging axiallythe fan bypass flow B pressurized by the upstream fan section 20 of theturbofan engine. A significant amount of thrust is provided by thebypass flow B due to the high bypass ratio. The fan section 20 of theengine 10 is preferably designed for a particular flightcondition—typically cruise at 0.8 M and 35,000 feet. The fan section 20includes fan blades which are designed at a particular fixed staggerangle for an efficient cruise condition. The FVAN 42 is operated to varythe fan nozzle exit area 44 to adjust fan bypass air flow such that theangle of attack or incidence on the fan blades are maintained close todesign incidence at other flight conditions such as landing and takeoff,thus enabling optimized engine operation over a range of flightcondition with respect to performance and other operational parameterssuch as noise levels. Preferably, the FVAN 42 defines a nominalconverged position for the fan nozzle exit area 44 at cruise and climbconditions, but radially opens relative thereto to define a divergedposition for other flight conditions. The FVAN 42 preferably provides anapproximately 20% (twenty percent) change in the fan nozzle exit area44. It should be understood that other arrangements as well asessentially infinite intermediate positions as well as thrust vectoredpositions in which some circumferential sectors of the FVAN 42 areconverged relative to other diverged circumferential sectors arelikewise usable with the present invention.

The FVAN 42 is preferably separated into at least four sectors 42A-42D(FIG. 1C) which are each independently adjustable to asymmetrically varythe fan nozzle exit area 44 to generate vectored thrust. It should beunderstood that although four sectors are illustrated, any number ofsectors may alternatively be provided.

In operation, the FVAN 42 communicates with a controller C or the liketo adjust the fan nozzle exit area 44 in a symmetrical and asymmetricalmanner. Other control systems including an engine controller or aircraftflight control system may also be usable with the present invention. Byadjusting the entire periphery of the FVAN 42 symmetrically in which allsectors are moved uniformly, thrust efficiency and fuel economy aremaximized during each flight condition. By separately adjusting thecircumferential sectors 42A-42D of the FVAN 42 to provide anasymmetrical fan nozzle exit area 44, engine bypass flow is selectivelyvectored to provide, for example only, trim balance, thrust-controlledmaneuvering, enhanced ground operations and short field performance.

Referring to FIG. 2A, the FVAN 42 generally includes a flap assembly 48which define the fan nozzle exit area 44. The flaps 48 are preferablyincorporated into the end segment 34S of the fan nacelle 34 to define atrailing edge 34T thereof. The flap assembly 48 generally includes amultiple of flaps 50, each with a respective linkage system 52 and anactuator system 54.

Each flap 50 defines a pitch point 56 about which the flap 50 pivotsrelative the fan nacelle 34 (best illustrated in FIG. 2B). Forward ofthe pitch point 56 relative the trailing edge 34T, the linkage system 52preferably engages the flap 50. It should be understood that otherlocations may likewise be usable with the present invention.

The linkage system 52 preferably includes a cable 58 which circumscribesthe fan nacelle 34. The cable 58 engages each flap 50 at a flapengagement point 60 and a multiple of fixed fan nacelle structures 34Rsuch as fan nacelle ribs or such like at a fixed engagement point 62.The flap engagement point 60 is preferably located within a flapextension 64 (FIG. 2B) which extends forward of the pivot point 56relative the trailing edge 34T and is preferably contained within thefan nacelle 34. It should be understood that various flap extensions 64and the like may be utilized within the flap linkage 52 to receive thecable 58 and that only a simplified kinematics representation isillustrated in the disclosed embodiment.

The cable 58 is preferably strung within the fan nacelle 34 to passthrough one fixed engagement point 62, the flap engagement point 60 anda second fixed engagement point 62 (FIG. 2C). That is, the flapengagement point 60 is intermediate the fixed engagement points 62. Thefixed engagement point 62 and the flap engagement point 60 are generallyeyelets or like which permit the cable to be strung therethrough. Theeyelets may include roller, bushing, or bearing structures whichminimizes friction applied to the cable 58 at each point 60, 62.Preferably, the cable 58 is strung through a multiple of flaps 50 todefine a flap set of each circumferential sectors 42A-42D of the FVAN42. That is, a separate cable 58 is utilized within each circumferentialsector 42A-42D such that each cable 58 is individually driven by theactuator system 54 to asymmetrically adjust the FVAN 42.

Preferably, the actuator system includes a compact high power densityelectromechanical actuator (EMA) 65 or a rotary hydraulic actuator whichrotates a spool 66 connected thereto. Alternatively, a linear actuatormay be also utilized to directly pull the cable 58 to change theeffective length thereof. That is, the cable 58 is pulled transverse tothe length thereof such that the overall length is essentially “spooled”and “unspooled.” It should be understood that a cable-driven systeminherently facilitates location of the actuator 65 relatively remotelyfrom the multiple of flaps 50 through various pulley systems and thelike. It should be understood that various actuator systems whichdeploys and retract the cable will be usable with the present invention.

Referring to FIG. 2C, the actuator system 54 engages an end segment 58Aof the cable 58 such that the cable 58 may be spooled and unspooled toincrease or decrease the length thereof. The cable 58 is wound around aspool 66 at one end segment 58A while the other end segment 58B isattached to a fixed attachment such as one of the fixed structure 34R.By spooling the cable 58 around the spool 66, the effectivecircumferential length of the cable 58 is effectively decreased (shownin phantom) such that the fan nozzle exit area 44 is decreased. Byunspooling the cable 58 from the spool 66, the effective circumferentiallength of the cable 58 is effectively increased (shown solid) such thatthe fan nozzle exit area 44 is increased. The bypass flow B permitsunilateral operation of the FVAN such that the bypass flow B divergesthe flaps 50 and the FVAN 42 need only be driven (cable 58 retracted) toovercome the bypass flow B pressure which results in a significantweight savings. This advantage of the present invention allows practicaluse of the variable area nozzle on the gas turbine engines.

Whereas the diverged shape is utilized for landing and takeoff flightconditions, should the cable 58 break, the FVAN 42 will failsafe to thediverged shape. It should be understood, however, that positive returnmechanisms may alternatively or additionally be utilized.

Each cable 58 preferably pitches one flap set between the convergedposition (shown in phantom) and a diverged position. It should beunderstood that although four sectors are illustrated (FIG. 1C), anynumber of sectors may alternatively or additionally be provided. Itshould be further understood that any number of flaps 50 may becontrolled by a single cable 58 such that, for example only, the singlecable may be strung around the entire circumference of the fan nacelle34, however, a sector arrangement is preferred to provide asymmetriccapability to the FVAN 42.

The foregoing description is exemplary rather than defined by thelimitations within. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, one ofordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

1. A nacelle assembly for a gas turbine engine comprising: a corenacelle defined about an axis for allowing flow to pass therethrough; afan nacelle mounted at least partially around said core nacelle, saidfan nacelle having a fan variable area nozzle that defines a fan exitarea between said fan nacelle and said core nacelle, said nozzle havinga plurality of pivotable flaps pivotable about a pivot defined by eachof said flaps; a cable passing through an orifice defined by at leastone of said flaps; and an actuator system operable to mechanicallyretract said cable therein pivoting at least one of said flaps aboutsaid pivot to lessen said fan exit area and mechanically extend saidcable to enable said flow to pivot at least one of said flaps about saidpivot and increase said fan exit area, wherein said actuator system isengaged with said cable, and a segment of said cable, opposite saidactuator system, is attached to a fixed structure.
 2. The nacelleassembly as recited in claim 1, wherein there is one actuator system forsaid plurality of flaps.
 3. The nacelle assembly as recited in claim 1,wherein said actuator system includes a spool configured to spool andunspool said cable.
 4. The nacelle assembly of claim 3, wherein spoolingof said cable around said spool decreases the fan nozzle exit area. 5.The nacelle assembly of claim 3, wherein unspooling of said cable aroundsaid spool increases the fan nozzle exit area.
 6. The nacelle assemblyas recited in claim 1, wherein said cable is strung through one of saidplurality of flaps intermediate a first fixed structure of said fannacelle and a second fixed structure of said fan nacelle.
 7. The nacelleassembly as recited in claim 6, wherein said first fixed structure ofsaid fan nacelle and said second fixed structure of said fan nacelleinclude a rib of said fan nacelle.
 8. The nacelle assembly as recited inclaim 1, wherein said fan variable area nozzle includes a multiple offlap sets, each of said flap sets separately driven by a respectivecable and actuator of said actuator system to adjust said fan variablearea nozzle.
 9. The nacelle assembly as recited in claim 8, wherein eachflap set corresponds to a circumferential sector of the fan variablearea nozzle.
 10. The nacelle assembly as recited in claim 9, whereinthere are four circumferential sectors.
 11. The nacelle assembly asrecited in claim 1, further comprising: a gear system driven by a coreengine; and a fan driven by said gear system about said axis.
 12. Thenacelle assembly as recited in claim 1, wherein the actuator systemincludes an electromechanical actuator.
 13. The nacelle assembly asrecited in claim 1, wherein the actuator system comprises a rotaryhydraulic actuator.
 14. An assembly for pivoting a flap, said assemblydisposed about an axis along which a flow passes from an upstreamdirection to a downstream direction, said assembly comprising: astructure mounted at least partially around said axis, said structureattached to a pivotable flap arranged to define a nozzle area, saidpivotable flap being pivotable about a pivot at said structure; a cableengaged with a first fixed engagement point of said structure, saidcable passing through an orifice defined by said flap; and an actuatorsystem operable to mechanically retract said cable therein to lessen thenozzle area and mechanically extend said cable to enable said flow tourge said flap to increase said nozzle area, wherein said actuatorsystem is engaged with said cable, and a segment of said cable, oppositesaid actuator system, is attached to a fixed structure.
 15. The assemblyas recited in claim 14, wherein said actuator system includes a spoolengaged with said cable.
 16. The assembly as recited in claim 14,wherein said cable is strung through said orifice intermediate saidfirst fixed engagement point and a second fixed engagement point of saidstructure.
 17. A method of providing a variable fan exit area of ahigh-bypass gas turbine engine comprising the steps of: (A) locating afan variable area nozzle to define a fan nozzle exit area between a fannacelle and a core nacelle; (B) disposing a cable through at least onenacelle engagement point of said fan nacelle and through at least oneflap engagement point of said fan variable area nozzle; (C) providing anactuator system that engages with said cable; (D) activating ordeactivating the cable engaged with said fan variable area nozzle tovary the fan nozzle exit area to adjust fan bypass airflow, whereindeactivating said cable extends the cable to enable said flow to urgesaid flaps to increase said area.
 18. A method as recited in claim 17,wherein said step (B) further comprises: (a) activating the cable toconverge the fan nozzle exit area during cruise flight condition.
 19. Amethod as recited in claim 17, wherein said step (B) further comprises:(a) engaging a first end of the cable at a spool and a second end of thecable at the fixed attachment point, wherein said cable between saidfirst and second ends is received in an orifice defined at said flapengagement point.
 20. A method as recited in claim 17, wherein theactuator system comprises a rotary hydraulic actuator.